In GB 2297989, is described a so-called continuous miner, in which the hitherto “dry” rotary cutting head, comprising a drive shaft carrying a centre drum and two, co-axial outer drums, is provided with a safe supply of pressurised water whereby, if and when a water leak occurs, there is no leakage eg into a gear box, but only to an exterior part of the cutting head, and hence onto the mine floor. It was envisaged in GB 2297989 that each of the three drums would have its own individual water feed by a cartridge unit. This system has been used in practice and has had some degree of success. Inevitably, rotary water seals wear requiring the dismantling or changing of the cartridges, but the changing of the central cartridge, which by necessity was constructed in two halves and built around the central drum, was a long labourious procedure.
An advantage of the original three-cartridge system was the phasing of the water on the heads. This was threefold:                to reduce the amount of water used;        to prevent the machine operator from getting wet; and        to encourage the movement of fresh air into a cut zone.        